Vacuum tubes such as diodes, triodes and tetrodes, normally operating on the principle of thermal electron emission, began a fall from favor with the discovery and implementation of semiconductor technology as exemplified by the transistor. Compared to their semiconductor counterparts, vacuum tubes had several limitations, including the likelihood of failure of the incandescent cathode due to thermal stress. In addition, as a result of the relatively large spacial distances employed, the tubes were also relatively slow. Such distances also required a relatively high vacuum to insure that an emitted electron would not encounter a residual atom or molecule in its travel to the tube anode. Lastly, the physical sizes of such tubes, along with their power requirements and heat dissipation, put severe limitation on their use in largescale switching or memory applications.
It is accordingly an object of the present invention to provide a new and improved version of a vacuum tube which has a cathode element which is not operated at elevated temperatures.
Yet another object of the present invention is to provide such a vacuum tube having a reduced geometric scale, allowing for providing improved response time and for greater packing.
Yet another purpose of the present invention is to provide an improved vacuum tube which may be constructed using advanced drawing and deposition techniques, allowing the tube to be formed at reduced expense and in a repetitive layout, allowing large-scale integrated circuits of such tubes to be created.